what is the perimeter of a square with a 64 square square foot radius

assuming you meant 64 square foot area (cuz i dunno how a square has a radius fam)

$${\sqrt{{\mathtt{64}}}} = {\mathtt{8}}$$

since is its a square, its side lengths can be found be square rooting the area
  $${\mathtt{8}}{\mathtt{\,\times\,}}{\mathtt{4}} = {\mathtt{32}}$$

then by multiplying by 4 

so the total perimeter of the square is 32 feet